Memory leak detection in React Native - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a memory leak in React Native?

A memory leak happens when the app keeps using memory that it no longer needs, causing the app to slow down or crash over time.

beginner

Why are memory leaks bad for mobile apps?

Because mobile devices have limited memory, leaks can make apps slow, use more battery, or crash, leading to a bad user experience.

intermediate

Name a common cause of memory leaks in React Native components.

Not cleaning up timers, subscriptions, or event listeners when a component unmounts can cause memory leaks.

intermediate

How can you detect memory leaks in a React Native app?

Use tools like React Native Debugger or Xcode Instruments to watch memory usage and find if memory keeps growing without releasing.

intermediate

What React hook helps prevent memory leaks related to side effects?

The useEffect hook with a cleanup function helps remove timers, subscriptions, or listeners when the component unmounts.

What happens if you forget to clear a timer in a React Native component?

A No effect on memory

B The app will automatically fix it

C The timer stops by itself

D Memory leak because the timer keeps running

If you don't clear timers, they keep running and hold memory, causing leaks.

Which tool can help you monitor memory usage in React Native?

A React Native Debugger

B Photoshop

C Excel

D Slack

React Native Debugger can show memory usage and help find leaks.

What should you do inside useEffect to avoid memory leaks?

A Return a cleanup function to remove side effects

B Do nothing

C Call setTimeout repeatedly

D Ignore component unmount

Returning a cleanup function removes timers or listeners when the component unmounts.

Memory leaks in mobile apps can cause:

A More storage space

B Faster app performance

C Slower app and crashes

D Better battery life

Leaks use memory unnecessarily, slowing the app and causing crashes.

Which of these is NOT a common source of memory leaks?

A Unremoved event listeners

B Properly cleaned up subscriptions

C Uncleared timers

D Retained references to unused objects

Proper cleanup prevents leaks; not cleaning up causes leaks.

Explain what a memory leak is in React Native and how you can prevent it.

Think about what happens when you forget to stop something running in your app.

Describe tools and methods you would use to detect and fix memory leaks in a React Native app.

Consider how you watch memory and clean up resources.